Abstract Heat transfer and pressure drop of turbulent fluid flow were studied numerically and experimentally in a quad-channel with twisted tapes placed in a circular tube under uniform heat flux boundary condition. All the tests were conducted with water as the working fluid where the turbulent flow range of Reynolds numbers were maintained at 4250 to 11000. Quad-channel twisted tapes (QCTT) were manufactured by 3D printer with the material PLA, the lengths of 50 mm, 100 mm, 200 mm with the twist ratio of 4.48. The tapes were identified with their tape/pipe length ratios (TPR) of 0.025, 0.05 and 0.1. Validation of the experimental data was performed by the comparison of the experimental results with the data from the well-known empirical correlations. Alteration of the friction factors and Nusselt numbers with the Reynolds numbers are presented in this paper. The results showed that the Nusselt number and the friction factor increased with the increasing of the length of QCTTs. On the other hand, the performance evaluation criteria (PEC) should be declining with the increase of the lengths of the tapes. The evaluated temperature distributions inside the tested tubes with the inserts were plotted in order to investigate the observed data. Based on the obtained experimental data, the empirical correlations for the Nusselt number within the deviation of ±2% and the friction factor within the deviation of ±5% were developed for the practical usage.

中文翻译：

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管内四通道双绞带插入件的单相流传热特性

摘要 在均匀热流边界条件下，在圆管中放置扭带的四通道中，对湍流流体的传热和压降进行了数值和实验研究。所有测试均以水为工作流体进行，雷诺数的湍流范围保持在 4250 至 11000。四通道双绞带（QCTT）由 3D 打印机制造，材料为 PLA，长度为 50 mm， 100 毫米、200 毫米，捻比为 4.48。胶带的胶带/管长度比 (TPR) 为 0.025、0.05 和 0.1。通过将实验结果与来自众所周知的经验相关性的数据进行比较来验证实验数据。本文介绍了摩擦因数和努塞尔数与雷诺数的变化。结果表明，随着QCTTs长度的增加，Nusselt数和摩擦系数增加。另一方面，性能评价标准（PEC）应该随着胶带长度的增加而下降。为了研究观察到的数据，绘制了带有插入件的测试管内的评估温度分布。基于获得的实验数据，建立了±2%偏差范围内的Nusselt数和±5%偏差范围内的摩擦系数的经验关系式，以供实际使用。性能评价标准（PEC）应该随着胶带长度的增加而下降。为了研究观察到的数据，绘制了带有插入件的测试管内的评估温度分布。根据获得的实验数据，建立了±2%偏差范围内的Nusselt数和±5%偏差范围内的摩擦系数的经验关系式，以供实际使用。性能评价标准（PEC）应该随着胶带长度的增加而下降。为了研究观察到的数据，绘制了带有插入件的测试管内的评估温度分布。根据获得的实验数据，建立了±2%偏差范围内的Nusselt数和±5%偏差范围内的摩擦系数的经验关系式，以供实际使用。